Methods and compositions are disclosed utilizing olanzapine-N-oxide for the treatment of psychosis in humans. Olanzapine-N-oxide exhibits a lessened liability toward drug-drug interactions than olanzapine and a more predictable dosing regimen than olanzapine. Olanzapine-N-oxide is also useful for the treatment of acute mania, mild anxiety states, anxiety disorders, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, autistic disorder, excessive aggression, substance abuse,...